I have never used or relied on the bubble level on the electric jack. I carry a small torpedo level with me that I keep in the lower shelf just to the left of the door.
I place the level close to the middle of the trailer, and level with the jack. It's more convenient to have a helper with booze in hand to let you know when you are level.
I have also found that if you place the torpedo level on the battery compartment top, that is about the same level-ness as putting it on tthe floor inside. It's more convenient too, but test one against the other.
As far as that light you write about, that's been a thorn in my ass forever. It would be real nice to just turn on a light in JUST the lav, instead of the whole coach, only to wake a cranky, growling wild beast, otherwise known as the wife.
My solution has been to use my AA Mag-lite flashlight, held in mouth while doing business, and hoping that it does not fall out injurying man-hood (what's left of it) or worse, illuminate the inner workings of the toilet!